Pipe laying and replacement

Abstract

Apparatus for use in the laying and/or replacement of pipes under ground comprises a casing (1), a frusto-conical impact member (2) secured to one end of the casing and adapted to form an underground passage for the casing when the apparatus is being driven through the ground, a piston (7) reciprocally mounted in the casing and arranged to be driven by a source of compressed air or other fluid to engage the impact member (2) with a series of impacts to drive said member and the casing through the ground and a control valve member (11) adapted to be connected to a source of compressed air or other fluid and arranged to reciprocate the piston in the casing by means of said compressed air or other fluid. A pipe fitting (31) is connected to a tubular spacer member (23) which is mounted on the other end of the casing (1), said pipe fitting being adapted to be clamped to the leading end of a pipeline (29 and/or 30) which is to be laid in the underground passage formed by the impact member (2). The connection between the pipe fitting (31) and spacer member (23) includes a flanged sleeve (25) which permits relative rotation between the pipe fitting and the casing.

I claim: 
     
       1. Apparatus for use in the laying and/or replacement of pipes underground which comprises a cylindrical casing, a conical or frusto-conical member secured to one end of the casing and adapted to form an underground passage for the casing when the apparatus is being driven through the ground, a piston reciprocally mounted in the casing and arranged to be driven by a source of compressed air or other fluid to engage said conical or frusto-conical member with a series of impacts to drive said member through the ground, means for connecting the interior of the casing to a source of compressed air or other fluid, valve means to ensure that the piston is reciprocated in the casing by said compressed air or other fluid, a pipe fitting for clamping to the leading end of a pipeline which is to be laid in the underground passage formed by said conical or frusto-conical member and a connection between the pipe fitting and the said other end of the casing, said connection comprising a sleeve connected to the said other end of the casing and having an internal flange, the pipe fitting being a free sliding fit in the sleeve to permit relative rotation between the pipe fitting and the sleeve, and hence the casing, and said pipe fitting being retained in the sleeve by projection means which are engageable with said internal flange of the sleeve. 
     
     
       2. Apparatus according to claim 1, wherein the sleeve is provided with a screw-thread by means of which it is secured to the said other end of the casing. 
     
     
       3. Apparatus according to claim 1, wherein the pipe fitting is provided with a screw-thread and said projection means comprise a lock nut which is engageable with said screw-thread. 
     
     
       4. Apparatus according to claim 3, wherein a thrust washer is provided, said thrust washer being located on the pipe fitting and arranged to be clamped between the flange on the sleeve and the lock nut. 
     
     
       5. Apparatus according to claim 1, wherein the conical or frusto-conical member is provided with a series of radially extending fins to aid in fracturing an existing pipe and to reduce the tendency of the apparatus to rotate in operation. 
     
     
       6. Apparatus according to claim 1, wherein the said one end of the casing is provided with a cavity adapted to receive one end of the piston, the other end of the piston being hollow and a first sleeve being slidably mounted in the said other end of the piston, a control valve member being mounted in said first sleeve and extending at one end into the said other end of the piston and the other end of the control valve member being adapted to be connected by a pressure line to said source of compressed air or other fluid, the control valve member further having an axial bore extending throughout its length. 
     
     
       7. Apparatus according to claim 6, wherein the control valve member is slidable with respect to the first sleeve and is held in position by a coil spring bearing at one end on the sleeve and at the other end on a thrust washer mounted on the control valve member. 
     
     
       8. Apparatus according to claim 7, wherein the first sleeve and the control valve member are provided with radial bores which are normally held out of alignment by the coil spring. 
     
     
       9. Apparatus according to claim 6, wherein the first sleeve is mounted on one end of a second sleeve through which the control valve member extends. 
     
     
       10. Apparatus according to claim 9, wherein the other end of said second sleeve is mounted in an elastic bearing which is mounted in a tubular spacer member secured to said other end of the casing. 
     
     
       11. Apparatus according to claim 10, wherein a seal is provided on said second sleeve, said seal being arranged to bear against the tubular spacer member to prevent the ingress of dirt and moisture into the interior of the casing while allowing compressed air or other fluid to escape from said casing. 
     
     
       12. Apparatus according to claim 10 wherein the said connection between the pipe fitting and the said other end of the casing includes said tubular spacer member which is provided with an external screw-thread at each end, one screw-thread being engageable with a corresponding internal screw-thread on the casing. 
     
     
       13. Apparatus according to claim 1, wherein the pipe fitting takes the form of a hollow sleeve having a tapered end which is adapted to be pushed into the end of a pipeline. 
     
     
       14. Apparatus according to claim 13, wherein a tapered sleeve is mounted coaxially on said hollow sleeve and is adapted to receive the end of a second pipeline having a larger diameter than that of the first-mentioned pipeline whereby two coaxial pipelines can be laid simultaneously. 
     
     
       15. Apparatus according to claim 14, wherein a collar having a depending skirt is provided on the pipe fitting, said skirt surrounding part of the length of the tapered sleeve whereby the end of said second pipeline can be gripped between the skirt and the said tapered sleeve. 
     
     
       16. Apparatus according to claim 13, wherein the pipe fitting is provided with an internal lug having a through-going bore for receiving a cable. 
     
     
       17. Apparatus according to claim 16, wherein one end of the cable is prevented from pulling through the bore in said lug, said cable being arranged to extend through a pipeline fitted to the pipe fitting and extending through a locking plate at the other end of said pipeline, means being provided for tensioning the cable against the locking plate. 
     
     
       18. Apparatus according to claim 17, wherein the cable tensioning means comprises a screw-threaded ferrule provided on the other end of the cable and engageable by a lock nut.